Hydrophobic composition and use on a substrate for preventing ice formation and corrosion

ABSTRACT

Graphite has a lubricating property resulting from its laminar structure in two planes, basal and edge plane. The basal plane is hydrophobic. The use of graphite or carbon treated at high temperature in a composite or coating (paint) whereof the privileged orientation of particles is basal enables to cause the coating to be water-repellent. Said property enables to prevent or reduce ice accumulation as well as corrosion on electrical installations.

FIELD OF THE INVENTION

[0001] The invention relates to compositions as well as a method forapplying same on a substrate to make the latter hydrophobic and toprevent ice formation and, eventually, ice accumulation thereon, as wellas its corrosion. More particularly, the invention concerns the use ofgraphite particles or crystallized carbon particles in a composite shapewherein the particles are oriented according to the basal plane, to makethe substrate, for example an electric conductor, hydrophobic, and thusprevent all damages caused by ice accumulation and corrosion.

BACKGROUND OF THE ART

[0002] Natural and artificial graphites occur in a flake shape with twosides, comprising a basal plane and a plane commonly called edge. Theseproducts, which are relatively cheap and constitute good lubricants, areused for various applications in the steel and automobile industries. Inthe field of energy stocking, the graphite composite is known for itsuse as an anode in rechargeable or lithium-ion batteries. In graphites,lithium intercalation is done through the edge planes and not throughthe basal planes. During the anode processing, the process compulsorilygoes through a calendering step, i.e. a lamination. This step,well-known to the man skilled in art, has for effect to orientate thegraphite particles according to the basal planes, which makes the anodesurface lubricating. In the battery industry, the addition of sphericalmetallic particles, carbon or the like, to the graphite compositeprevents the orientation of the basal plane during the calendering.Graphite basal planes have an hydrophobic property which depends on thecrystallinity of the carbon used. To increase this crytallinity, it ispossible to process the carbon at a temperature higher than 1800° C.

[0003] Ice accumulation on electric installations or the like such asbridges, circulation lights, boats, etc. located in Nordic regionsconstitutes a major problem which can cause considerable damages, notonly thereon, but on the whole network. Such accumulation, if it is notcontrolled, creates an excess weight which can cause failures on thetransport and distribution electrical network, and ultimately involveheavy consequences due to its nature as a motor of the economy andpublic life of the electrical network. Protection of the electricalnetwork as well as all other installations exposed to ice accumulationis therefore primordial. The approaches proposed in the aviation toprevent ice accumulation are of a mechanical, chemical or thermal type.Graphite has been used in the thermal approach in an amorphous shape(expanded graphite).

[0004] There therefore exists a need to resort to an efficient and cheaptechnique allowing to protect electrical distribution lines against iceformation during cold periods and corrosion.

SUMMARY OF THE INVENTION

[0005] The present invention has for object the use of the lubricatingproperty of graphite due to its laminar structure with two planes, basaland edge, and other substances having the same property, to protectelectrical networks from ice formation and corrosion.

[0006] The invention also has for object to use the basal plane ofgraphite which makes the latter hydrophobic in the battle against iceformation and corrosion on a metallic substrate.

[0007] Another object of the invention consists in using thepreferential basal orientation of graphite particles or carbon particlestreated at high temperature to repel water on a coating surfacecomprising graphite or carbon treated at a high temperature.

[0008] The invention concerns a composition intended for coating asubstrate to make the latter hydrophobic and/or prevent ice formationand, eventually, ice accumulation thereon, and corrosion of the latter.The composition comprises particles as well as a vehicle in which theparticles are incorporated, and is characterized in that the particlescomprise at least one surface making them hydrophobic, and are orientedaccording to said surface when they are incorporated in the vehicle.

[0009] The invention also concerns a method for using this compositioncharacterized in that the composition is applied on a substrate and thecomposition thus applied is treated to generate an hydrophobic andanti-corrosive coating.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010]FIG. 1 is a schematic illustration showing the graphiteexfoliation; and

[0011]FIG. 2 is an enlargement of exfoliated graphite particles, showingbasal and edge planes.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] According to a preferred embodiment of the invention, theparticles have a crystalline structure and possess at least one cleavageplane that makes them hydrophobic. For example, all of them have a basalplan that makes them hydrophobic.

[0013] Advantageously, the particles comprise crystallized carbon,especially graphite or carbon processed at a temperature high enough tomake it crystalline, the particles being oriented according to the basalplane. If graphite is used, it is advantageous that the latter has ahigh purity level, particularly at least 99.9%. It is indeed desirablethat graphite practically contains no substances provokingnon-conductivity, corrosion, or oxidation of the substrate on which itis deposited. Preferably, an exfoliated graphite is used.

[0014] When using a graphite in the composition according to theinvention, it is advantageous to make the particles still morehydrophobic than what is yield by the basal plane. To achieve this, itis possible to add a fluorinated compound having the formula C_(x)F_(y)where x and y are integers, especially CF, C₂F, C₄F. This compound canreduce the negative effect on the particle hydrophobia, particularly atthe level of the edge sides.

[0015] The same results would be obtained by using a compound having aformula MF_(z), where M represents an alkali or alkaline-earth metal andz represents 1 or 2. For example, it is possible to use CaF₂, BaF₂, LiFor a mixture thereof. The graphite such as purified by the Hydro-Quebecprocess (see PCT/CA01/00233) shows, on the surface, the presence offluorinated hydrophobic compounds of the type CaF₂ and the like, whichcauses an increase of the hydrophobia level by using graphite purifiedby the process mentioned in this patent.

[0016] The particles may also be formed of carbon fibers and they arethen oriented in the vehicle in the direction of the fiber length.

[0017] The vehicle advantageously comprises an hydrophobic polymercapable of forming a composite with the particles.

[0018] Practically, it is preferable to use graphite particles having asize ranging between approximately 0.5 μm and 350 μm, a purity levelranging from 95 and 99.99% and an interplanar spacing d002 rangingbetween 3.35 to 3.40.

[0019] According to another preferred embodiment of the invention, thecomposition comprises a dispersion of graphite particles described inthe previous paragraph in a solution comprising the hydrophobic polymeracting as a binder for the particles to constitute the composite.Advantageously, the graphite is present in the composition in a ratioranging from 5 to 95% by weight.

[0020] According to another preferred embodiment of the invention, thepolymer comprises a polyvinylidene fluoride, a polyvinylidene chloride,or a polytetrafluoroethylene, or a mixture thereof.

[0021] The composition can also comprise a simple dispersion of graphiteparticles in a random polymer, especially an ethylene oxide andpropylene oxide copolymer, in a ratio ranging from 5 to 95% by weight.

[0022] The composition can also comprise a dispersion of graphiteparticles with a binder, preferably UV stable, intended to constitutethe composite. This composite is then introduced in a solvent toconstitute a painting. For example, the binder can comprise a polyester,a polyurethane, a polyacrylate or paraffin.

[0023] The composition can also comprise an additive promoting the flowand the flotation of graphite particles according to the basalorientation, particularly Teflon® or a stearate.

[0024] Another embodiment of the invention is that the compositioncomprises especially a melted mixture of graphite powder, solid and UVstable polymer resin, and solid additives, the mixture being grinded andconditioned for an application with an electrostatic rocket on ametallic substrate.

[0025] According to another embodiment, the type of graphite used is anexfoliated graphite. The use of this exfoliated graphite (FIG. 1),obtained following PCT/CA01/00233, in the composite increases thefraction of basal surfaces and reduces the edge ones such as detailed inthe model (FIG. 2). Moreover, the addition of CaF₂ or anotherhydrophobic material can be interesting for coating the remaining edgesides to obtain a completely hydrophobic surface.

[0026] According to another preferred embodiment of the invention, thecomposition according to the invention is treated by flotation, bypressure or by a combination flotation-pressure to obtain a basalorientation of the particles, and the composition thus treated isapplied on a substrate in a mechanic and/or an electrostatic manner tomake an hydrophobic and anti-corrosive coating.

[0027] The choice of the binder used in the composite is important, thelatter must also have an hydrophobic property (Teflon™, polyester,alkane or other binder). Optimization of the size of graphite particlesplays an important role in the coating homogeneity and in thehydrophobic aspect, such as it appears obvious to the man skilled in theart. The orientation of graphite particles according to the basal planeis made by flotation or by pressure exerted on the composite.

[0028] Such as described above, the composite particularlygraphite-polymer can be used as such with or without solvent, or as apaint, with or without solvent.

[0029] For example, if it is desired to use it with a solvent, agraphite powder is dispersed in a solution using a binder dissolved in asolvent or a mixture of solvents. This binder can be of a polyvinylidenefluoride (PVDF) type, a polyvinylidene chloride (PVC) type, or apolytetrafluoroethylene (PTFE) type, or the like. The composition cancomprise between 5% to 95% by weight of graphite. Spreading is made on astrip or a support by the Doctor Blade™ method, followed by calendaringon the same line. The film surface becomes bright, which is a sign ofthe basal orientation of the graphite particles.

[0030] If it is preferred to use a composite without solvent, it ispossible, for example, to disperse the graphite powder in a polymersolution of a random ethylene oxide and propylene oxide copolymer typePEO/PPO. The graphite composition can vary between 5% and 95% by weight.Spreading is made on a strip or a support by the Doctor Blade™ method,followed by calendaring on the same line. The film surface becomesbright, which is a sign of the basal orientation of the graphiteparticles.

[0031] In a painting with a solvent mode, the method could consist indispersing the graphite powder with a binder of a polyester, apolyurethane, an acrylate, an alkane or other UV stable binder type, ina solvent. Additives are added to this mixture to improve the flow andthe flotation of graphite particles according to the basal orientation.The additives are of a diluting liquid type or of a polymer type, suchas Teflon™, stearate or the like. The percentage of graphite depends onthe desired conductivity.

[0032] Another way to use the painting mode is to use the compositewithout solvent. For example, this method consists in mixing and meltinggraphite powder and polymer resin of a polyester type, UV stablepolyurethane with solid additives of a Teflon™, a stearate or the like.This graphite/resin mixture is grinded into a powder. The latter must beapplied with an electrostatic rocket on a metallic substrate. Duringpolymer melting, graphite particles are aligned according to the basalplane.

EXAMPLES

[0033] The invention will now be illustrated by the following examples,given as an illustration of the invention and without limitation.

Example 1

[0034] The PVDF binder is solubilized in NMP (n-methyl pyrrolidone). Amixture 80/20 of the acetone/toluene solvents is added to the paste PVDFNMP to form the spreading composition. The graphite powder is dispersedin the spreading composition in a weight ratio 90:10. This mixture isapplied on a copper collector by the Doctor Blade™ method. The electrodeis dried with an infra-red lamp at 65° C., followed by calendaring onthe same manufacturing line. The surface of these graphite films hashydrophobic properties.

Example 2

[0035] In this example, two mixtures (A) and (B) are prepared. Mixture(A) is composed of polyester, thermosealable resin and 20% of TiO₂ and2-6% by weight of graphite. The mixture (B) is composed of athermoplastic resin and 10 to 20% by weight of graphite. Both compoundsare extruded and pulverized separately. 85% of compound (A) is mixedwith 15% of compound (B). This powder is applied by an electrostaticprocess on a substrate. The latter is exposed to heat in order to meltand cook the powder.

[0036] Although the present invention has been described with specificimplementations, it understood that several variations and modificationscan be grafted to said implementations, and the present application aimsto cover such modifications, uses or adaptations of the presentinvention following, in general, the invention principles and includingall variations of the present description which will become known orconventional in the activity field in which the present invention isfound, and which can be applied to the essential elements mentionedabove, in accordance with the scope of the following claims.

1. Composition intended to coat a substrate to make the latterhydrophobic and prevent ice formation and eventually ice accumulation onsaid substrate and corrosion of the latter, said composition comprisingparticles as well as a vehicle comprising an hydrophobic polymer inwhich the particles are incorporated, characterized in that saidparticles have a crystalline structure and have at least one cleavageplane making them hydrophobic, said particles being oriented accordingto said cleavage plane when they are incorporated in said vehicle. 2.Composition according to claim 1, characterized in that said particleshave a basal plane, said basal plane constituting said cleavage planemaking said particles hydrophobic.
 3. Composition according to claim 2,characterized in that said particles comprise crystallize carbon whereinthe particles are oriented according to the basal plane.
 4. Compositionaccording to claim 3, characterized in that said crystallize carboncomprises graphite.
 5. Composition according to claim 3, characterizedin that said crystallize carbon comprises exfoliated carbon. 6.Composition according to claim 5, characterized in that the graphiteused is 99.9% pure.
 7. Composition according to claim 6, characterizedin that the exfoliated graphite comprises edge sides and the latter arecoated with a fluorinated compound of formula C_(x)F_(y) where x and yare numbers higher than or equal to
 1. 8. Composition according to claim4, characterized in that in addition to graphite, said compositecomprises a fluorinated compound of formula C_(x)F_(y) where x and y arenumbers higher than or equal to
 1. 9. Composition according to claim 4,characterized in that in addition to graphite, said composite comprisesa compound of formula MF_(z) where M is an alkali or alkaline-earthmetal and z represents 1 or
 2. 10. Composition according to claim 7,characterized in that said MF_(z) formula compound is selected fromCaF₂, BaF₂, LiF or a mixture thereof.
 11. Composition according to claim1, characterized in that the particles are formed of carbon fibers andare oriented in said vehicle along said fibers.
 12. Compositionaccording to claim 1, characterized in that said vehicle comprises anhydrophobic polymer capable of forming a composite with said particles.13. Composition according to claim 11, characterized in that theparticles are graphite particles having a size ranging betweenapproximately 0.5 μm and 350 μm, a purity level ranging between 95 and99.99% and an interplanar spacing ranging between 3.35 and 3.40. 14.Composition according to claim 12, characterized in that it comprises adispersion of graphite particles in a solution comprising said polymeracting as a binder for said particles to constitute said composite. 15.Composition according to claim 13, characterized in that the graphite ispresent in the composition in a ratio ranging from 5 to 95% weight. 16.Composition according to claim 14, characterized in that the polymer isselected from polyvinylidene fluoride, polyvinylidene chloride, orpolytetrafluoroethylene.
 17. Composition according to claim 12,characterized in that it comprises a simple dispersion of graphiteparticles in a random liquid copolymer, in a ratio ranging from 5 to 95%weight.
 18. Composition according to claim 16, characterized in that thecopolymer is an ethylene oxide and propylene oxide copolymer. 19.Composition according to claim 12, characterized in that it comprises adispersion of graphite particles in a solvent comprising a binderintended to constitute said composite.
 20. Composition according toclaim 18, characterized in that said binder is UV stable. 21.Composition according to claim 19, characterized in that said binder isselected from a polyester, a polyurethane, a polyacrylate and paraffin.22. Composition according to claim 20, characterized in that itcomprises an additive promoting the flow and the flotation of graphiteparticles according to the basal orientation.
 23. Composition accordingto claim 21, characterized in that the additive is selected from Teflon™and a stearate.
 24. Composition according to claim 12, characterized inthat it comprises a melted mixture of graphite powder, solid and UVstable polymer resin, and solid additives, the mixture being grinded andconditioned for an application by an electrostatic rocket on a metallicsubstrate.
 25. Method to prevent ice accumulation and/or corrosionformation on a substrate, characterized in that a composition accordingone of the claims 1 to 24 is applied on a substrate and the compositionapplied is processed to make an hydrophobic and anti-corrosive coating.26. Method to prevent ice accumulation and/or corrosion formation on asubstrate, characterized in that a composition according to one of theclaims 2 to 10 is processed by flotation, by pressure or by aflotation-pressure combination to obtain a basal orientation of saidparticles, said composition thus processed is applied on a substratemechanically and/or electrostatically to make an hydrophobic andanti-corrosive coating.
 27. Use of a composition according one of theclaims 1 to 24 to coat a substrate to prevent ice accumulation and/orcorrosion formation on said substrate.